1. Field of the Invention
This invention relates to exposure control apparatus for video cameras, still cameras and cinecameras, and more particularly to exposure control apparatus for cameras and flash devices in combination. The flash device may be incorporated into the camera, or may be an independent unit attachable to or connectable with the camera.
2. Description of the Prior Art
In the art of video cameras, the luminance signal obtained from the video signals of the image pickup means has been used to operate a servo drive for the diaphragm, or an auto-iris has been employed. Such system is proposed in, for example, U.S. Pat. No. 3,652,154.
To make a still picture, however, the auto-iris which controls the diaphragm by the use of a brightness (luminance) signal produced each 1/60 sec. is very slow in responding to changes of the brightness of the object being photographed and cannot provide a proper exposure immediately after the release. Also when an exposure is to be made with the use of a flash device, it is impossible to effect a proper flash exposure with an auto-iris.
When video having an auto-iris is used with flash or other artificial illumination, as the conditions of the object to be photographed change, the position of the diaphragm and the gain of the signal processing circuit is changed. In this case, if the responsiveness to such changes in the diaphragm position and the gain are very quick, the signal will assume a proper level. The auto-iris must, however, be moved by a servo system having a long time constant adapted to motion picture photography. In actual practice the long time constant has an adverse effect upon a flash exposure and results in the video signals assuming an improper level.